Aircraft engines and other aircraft components generate waste heat. If the waste heat is not disposed of, the components can fail from overheating, which has the potential to result in the loss of the aircraft. One way of disposing of waste heat is to force ambient air to enter an intake aperture, causing waste heat to be carried away with the exhaust of the air. Such “ram air” methods carry a drag penalty, however.
An aircraft's fuel can be also used as a heat sink for thermal management in modern high-performance aircraft designs. Waste heat absorbed to fuel can be exhausted with the combustion of the fuel. Fuel serves as a convenient resource and offers the benefits of minimizing or eliminating ram air drag penalty, which further results in a reduced radar signature for higher survivability. High performance legacy fighter aircraft, such as the F-18, F-22 and F-35, use fuel as a primary and secondary heat sink for their thermal systems.